The amount of extra shellscript for this is pretty daunting.

I commented on the issue that an environment variable would be way easier to integrate.
If you want to use shellscript for this, then it would be very nice to refactor this into a single file and include it somehow.

Very good point, an environment variable would make everything easier and would not require input from the user. I will adapt.

Switched to:

if [ -z "${PRECICE_TUTORIALS_NO_VENV:-}" ]
then
    python3 -m venv .venv
    . .venv/bin/activate
    pip install -r requirements.txt && pip freeze > pip-installed-packages.log
fi

(we already use this form just fine in the OpenFOAM adapter Allwmake)

Examples:

• ./run.sh: Installs and runs
• PRECICE_TUTORIALS_NO_VENV="" ./run.sh: Installs and runs
• PRECICE_TUTORIALS_NO_VENV="true" ./run.sh: Skips install, but runs

Notes:

• Because we set -u, we cannot use the -v option without additional handling. Calling ./run.sh would give PRECICE_TUTORIALS_NO_VENV: unbound variable. A workaround based on a default value (:-) would defeat the purpose.
• Kept the built-in [ test instead of the bash [[ test for consistency with the rest of the scripts (not needed here anyway).